This invention concerns in general a safety wheel providing improved traction and performance. In particular, a circular wheel is integrally formed with a tread design on its surface, with the tread design defining interstitial spaces. The tread design portion of the wheel is formed with a relatively hard material, while the interstitial spaces are filled with a relatively soft material integrally bonded to the harder material. This provides an overall smooth surface for the wheel while the relatively soft material absorbs unevenness in surfaces traversed by the wheel. Also, the use of different materials on different portions of the wheel can provide enhanced performance and/or interesting visual effects.
Another feature of one embodiment of this invention is that the relatively soft material may fill the interstitial spaces so as to form a slightly cupped area, thereby providing a suction cup effect for the wheel with respect to surfaces traversed thereby.
Various attempts have been made by prior inventors to provide a wheel having enhanced safety by including particular stone rejection features or improved handling or wear characteristics. Examples of U.S. Pat. Nos. disclosing such inventions are:
______________________________________ Inventor U.S. Pat. No. Issue Date ______________________________________ Heitfield 4,070,065 January 24, 1978 Youngblood 3,608,602 September 28, 1971 Hoke 3,727,661 April 17, 1973 Hoke 3,706,334 December 19, 1972 Hechinger 4,208,073 June 17, 1980 Fowlkes 2,878,071 March 17, 1959 Jones 322,611 July 21, 1885 Board 782,318 February 14, 1905 Okazaki 4,385,653 May 31, 1983 Pierson 4,478,266 October 23, 1984 ______________________________________
Heitfield discloses a particular wheel for use with skateboards and roller skates, wherein the wheel is a molded plastic wheel having a thin annular groove extending inwardly from its outboard end. The result is a resiliently yieldable and radially thin peripheral tread portion backed up by a thick relatively rigid band of material on the radially inward side of the groove. With such structure, Heitfield creates a soft wheel effect with a wheel of relatively hard plastic material.
Youngblood discloses a tire tread providing enhanced stone rejection. "Dimpled" mold insert blades are used to create relatively deep grooves having annular ridges and matching channels. The deep grooves enhance stone rejection while also permitting easier extraction of the tire from its mold.
Both Hoke patents are concerned with a tread design having grooves therein. The grooves have crossbar members at the bottom thereof which are integrally formed with the grooves themselves (i.e., all of the same one material). The grooves and the crossbars interact to capture and cradle stones therein so as to protect the remainder of the tire tread.
Hechinger discloses a wheel for skateboards made of a composite of low and high friction coefficient materials, i.e. urethane and rubber. The construction, however, requires a hub having projections to lock the rubber to the urethane.
Fowlkes discloses a laminated skate wheel having an inner annular softer portion disposed between two annular outer portions of a harder material. The various layers are fused together in a molding process. The purpose is to retain sufficient traction while obtaining increased wear characteristics.
Jones and Board disclose constructions which involve metal wheels having perforations or apertures into which a softer material is pressed.
Okazaki and Pierson disclose rubber tires formed of two different kinds of rubber, parallel strips in Okazaki and concentric strips in Pierson.
None of the prior art patents disclose a wheel having an interstitial construction of two different hardness materials in which the materials are integrally bonded to one another. Further, none of the prior art discloses an arrangement of a wheel using an interstitial construction of two different materials in which the two different materials can also be visually different, i.e. different colors, so as to obtain interesting visual and/or animation effects as the wheel rolls.
The present invention addresses these drawbacks and overcomes the same by utilizing two materials of different hardness (i.e., density) interstitially bonded in the fabrication of a whole. The harder of the two materials (i.e. the more dense) is used to form a tread design on the surface of the wheel. The less hard of the two materials (i.e. the less dense one) is then used to fill in interstitial spaces of the tread design in an integrally bonded relationship formed with the harder material. Additionally, the less hard material may be used to form the tread design, with the harder material filling in the interstitial spaces of the tread design. The overall surface of the resulting wheel is relatively smooth. However, the softer material filling the interstitial spaces of the tread design absorbs unevenness occurring in surfaces traversed by the wheel. Such unevenness might be caused by small stones or the like.
Furthermore, with some embodiments of the present invention, the interstitial spaces may be so formed by the tread design and filled with the softer material that a plurality of suction cup devices are formed on the surface of the wheel. These suction cup devices perform like any other suction cup to provide traction for the wheel on surfaces traversed thereby, especially when such surfaces are relatively smooth ones such as finished concrete.
Additionally, the two materials forming the interstitial construction may be provided with different visual characteristics, such as color, so as to obtain interesting visual and/or animation effects as the wheel rolls.
The features of this invention are applicable to virtually any type of tire or wheel, including but not limited to skateboard wheels, roller skates, bicycle tires, automobile tires and motorcycle tires.